1. Field of the Invention
The present invention relates to a process for producing a porous ceramic body for use as filters to collect fine particle from the exhaust gas of internal-combustion engines or as catalyst carriers.
2. Description of the Related Art
Because of the low strength of peripheral portions of a porous ceramic body having a three-dimensional network structure, the ceramic body has hitherto been produced by the following processes or the like. One of the processes, as disclosed in Japanese Patent KOKAI (Laid-Open) No. 176,110/82, comprises the steps of wrapping an organic foam of three-dimensional network or reticulate structure, which is a starting material for porous ceramics, with another organic foam which is finer in cell sizes than the former, and applying a ceramic slurry into the outer foam. Another one of the processes, as disclosed in Japanese Patent KOKAI (Laid-Open) No. 151,381/83, comprises the step of impregnating the peripheral portion of said starting material foam directly with a dense ceramic slurry.
According to these processes, a skin layer having a fine texture is formed around a porous ceramic body.
However, these processes involve such problems that the operation to form the skin layer is very complicated, and that the skin layer is liable to be separated from the porous ceramic body.